16:10
Session 7: Thermoplastic Composites
Chair: Ashley Chadwick
16:10
20 mins
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Automated Ply Placement, the established way to make high-rate composite parts
Marcus Kremers
Abstract: Automated Ply Placement, the established way to make high-rate composite parts
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16:30
20 mins
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Experimental and Numerical Study of CF/PEEK Composites in Laser-Assisted Tape Placement with Heated Tool Temperature Above Tg
Hong Ma, Aswani Kumar Bandaru, Paul Weaver
Abstract: The optimisation of process parameters in laser-assisted tape placement (LATP) for CF/PEEK composites has been widely studied; however, controlling the final composite properties remains challenging due to the inherently rapid heating and cooling rates. In this work, a heatable tool was introduced during manufacturing to regulate crystalline morphology and associated properties by maintaining the tool temperature within the crystallisation range of the matrix. Raising the tool temperature to 200 °C increased the average spherulite size substantially and the crystallinity from 34% to 37%. Numerical simulations revealed that in conventional LATP (without a heated tool), the tape surface temperature decreases rapidly to ~220 °C upon exiting compaction by the roller. By contrast, with a tool temperature of 200 °C, the temperature drop was limited to ~285 °C, arising from the significantly reduced the temperature difference between the incoming tape and substrate before nip point. This enhanced thermal profile promoted polymer diffusion, reduced interlaminar void content, and improved crystallisation. Transmission electron microscopy further confirmed the formation of a distinct diffusion region at tool temperatures above Tg, characterised by intermediate oxygen and carbon concentrations between fibre and matrix. These microstructural changes in crystalline morphology, void distribution, and interfacial structure were found to strongly influence the mechanical performance, including interlaminar shear strength and fracture toughness of CF/PEEK composites. Such findings are expected to provide new insights into optimising the performance of CF/PEEK composites manufactured by LATP through controlled microstructure, by introducing additional energy sources to address the intrinsic rapid heating and cooling rates without requiring major modifications to the LATP process.
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16:50
20 mins
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Therplastic composite cylindrical shell made by 4D printing
Suong Hoa, Mahmoud Fereidouni
Abstract: 4D Printing of Composites (4DPC) is a technique of composites manufacturing where structures of complex shape can be made without the use of molds of complex shapes. Only a flat mold is used. The technique has been used to make structures such as cylindrical shell, conical shell, S shaped structure, leaf spring, omega stiffener, letters of the alphabet, corrugated core for flexible wing, and vertical wind turbine blades [1]. These have been made using thermoset composites such as carbon/epoxy, which are composite prepregs that have been used to make aircraft structures. The principle of the method depends on the anisotropy of the laminate where layers of different fiber orientations interact with each other when the composite laminate is cooled from cure temperature to room temperature. For thermoset composites such as carbon/epoxy, after the resin is cured (usually at about 177 oC) the laminate is rigid during the whole period of cooling from cure temperature down to room temperature (20 oC). As such, the interaction between the layers of different fiber orientations is effective throughout this temperature range.
While thermoset composites can be used in many aircraft applications, for space applications, the problem of outgassing can be an issue. This and consideration for recycling lead to consideration to use thermoplastic composites. However, during the cooling from melt down to room temperature, thermoplastic composites exhibit stress relaxation. This gives rise to the variation of properties such as moduli not only due to the temperature change, but also due to the viscoelastic nature of the material. In addition, the use of automated fiber placement (AFP) machine to make the structure gives rise to additional issues such as variation in temperature gradients which in turn creates distortion.
The work presented by this abstract investigates different aspects of manufacturing unsymmetric laminates of thermoplastic composites using an AFP machine. The possibility of using laminate theory to predict the final shape of cylindrical shells is examined. The results are compared with results obtained from an elaborate experimental set up to measure the radii of curvature of the laminate at different temperatures.
References: 1. Suong Van Hoa, 4D Printing of composites, De Gruyter, 2025.
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17:10
20 mins
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Improving Interlayer Bonding in Thermoplastic AFP Through Vibration-Assisted Thermal Bonding and Repass Strategies
Arash Khodaei, Allyson Fontes, Farjad Shadmehri
Abstract: Automated Fiber Placement (AFP) of thermoplastic composites presents a promising route toward more energy-efficient manufacturing, primarily by allowing consolidation to occur in-situ and eliminating the need for secondary autoclave processing. Despite this advantage, key challenges remain, particularly in achieving high interlaminar bond quality. Rapid processing conditions often limit intimate contact and polymer chain diffusion at ply interfaces, leading to lower interlaminar strength and stiffness compared to autoclave-reconsolidated laminates.
To address these bonding deficiencies, this work introduces vibration-assisted thermal bonding (VATB) as an innovative approach to enhance interlayer consolidation in thermoplastic composites. Experimental evaluation through lap shear testing, supported by microstructural characterization, indicates that controlled vibration facilitates improved polymer mobility and interfacial diffusion. The application of VATB in both bonding and repair scenarios demonstrates increased bond strength along with reduced void content. In addition, the influence of repass as an in-situ technique is examined, with its effects on lap shear performance analyzed through mechanical testing and micrographic observations.
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